How can I make a class or object immutable

In this Q&A, we'll go over how to make a class immutable.

Object is immutable if its state  cannot be modified after its constructed.  This can be achieved by

• Making the member variable private and final
• initializing the member variable in the constructor and
• not exposing any setter methods

See the example below 

package com.javahowdoi.thread;

public class Immutable {

    final private int i;

    public Immutable(int i) {

        this.i = i;

    }

    public int getI() {

        return i;

    }

}